Palladium precipitation by formic acid

[Yggdrasil]

Then ill go directly with concentrated nitric acid and ill give high heat for 2 to 3 hours
Tin will be turned to insoluble metastannic acid and most of the nickel will not be dissolved
Mostly Silver copper and palladium will be in the solution.
After filtration ill precipitate silver with enough amount of hcl
Then collect my silver and precipitate palladium with formic acid using your way.
You mentioned that copper will not precipitate if the ph is around 2

Concentrated Nitric will dissolve Pd.
If you have Tin use HCl first, it will dissolve the Tin and most if not all the Nickel.
Filter it and wash the powder well, roast them and then go for Nitric, but use dilute Nitric, to reduce dissolving too much Pd.

 

[orvi]

Concentrated Nitric will dissolve Pd.
If you have Tin use HCl first, it will dissolve the Tin and most if not all the Nickel.
Filter it and wash the powder well, roast them and then go for Nitric, but use dilute Nitric, to reduce dissolving too much Pd.

Yeah, nitric dissolve bare, exposed Pd, but from my experience, platelets of ultrafine foils of Pd between layers of ceramic are very difficult to strip of values completely with nitric alone. That is why we completely abandoned "wet route" for MLCCs in classical terms of soaking the vigorously stirred powdered MLCCs in ntric. Without decomposition of ceramic matrix, it took ages for them to dissolve, even in hot solutions, and ceramics hold the values adsorbed onto the surface. HCL does much better job in destructing ceramic matrix, so AR leach is in my opinion necessary as second step.*

Owltech has relatively recently posted great video on processing old Bulgarian MLCCs by "wet route", altough he dissolve ceramic matrix firstly with conc. HCL - which also took with it base metals from the solder, and also somehow copper legs too. Mystery to me how copper can be dissolved in just HCL, but it is clearly happening in the conditions used, together with prolonged boiling. Important to say, if base metals dissapear from the solution, HCL also leach some Pd into the solution just by itself. So testing with stannous should be advised.

*edit for clarification: not all types of ceramic are decomposed in hot HCL or AR. Easiest to disintegrate and eventually dissolve are BaTiO3 ceramics found in old MLCCs. Altough some modern types are also attacked.

 

[Yggdrasil]

I agree, but Sayf wanted to go directly to concentrated Nitric and then in retrospect deal with the meta stannic acid.
That was the reasoning for my reply.
Edit for spelling.

 

[kurtak]

Owltech has relatively recently posted great video on processing old Bulgarian MLCCs by "wet route", altough he dissolve ceramic matrix firstly with conc. HCL

Orvi - could you provide a link to that video

I have a hard time believing you can dissolve ceramic with HCl

I have leached a lot of ceramics over the years (MLCCs, CATs, CPUs, ICs) & I have never seen HCl dissolve the ceramic - ever if very finely ground to powder

Are you sure he is not using HF (Hydrofluoric acid)

HF would certainly dissolve ceramic - especially if ground very fine

BUT - holy crap - what an extremely dangerous way to get rid of ceramic

HF is one (if not the) most dangerous acids on the planet

Kurt

 

[Alondro]

Orvi - could you provide a link to that video

I have a hard time believing you can dissolve ceramic with HCl

I have leached a lot of ceramics over the years (MLCCs, CATs, CPUs, ICs) & I have never seen HCl dissolve the ceramic - ever if very finely ground to powder

Are you sure he is not using HF (Hydrofluoric acid)

HF would certainly dissolve ceramic - especially if ground very fine

BUT - holy crap - what an extremely dangerous way to get rid of ceramic

HF is one (if not the) most dangerous acids on the planet

Kurt

I've actually encountered this with SOME ceramic MLCCs. The ceramic appears to be pure titanium oxide, and not as solid as other MLCCs. When broken, it has a 'powdery' look and not glassy. A few days in concentrated HCl, and those crumbled into white powder. Others of the harder, glassier type stayed intact. They didn't dissolve, but they did completely fall apart. So any metal layers inside would clearly also have been dissolved.

But since picking those out of a big batch is rather absurd, better to just smash them all up in the first place!

 

[orvi]

Orvi - could you provide a link to that video

I have a hard time believing you can dissolve ceramic with HCl

I have leached a lot of ceramics over the years (MLCCs, CATs, CPUs, ICs) & I have never seen HCl dissolve the ceramic - ever if very finely ground to powder

Are you sure he is not using HF (Hydrofluoric acid)

HF would certainly dissolve ceramic - especially if ground very fine

BUT - holy crap - what an extremely dangerous way to get rid of ceramic

HF is one (if not the) most dangerous acids on the planet

Kurt

I should say first that my previous post was maybe not clear enough, so I clarify what I wanted to say. Of course, you are right, not many ceramics can be dissolved in HCL.
In the video, Owltech disintegrated and eventually dissolved the ceramics from old MLCCs, but these are mainly barium titanate ceramics. Which disintegrate relatively easily in hot strong HCL solution. At least, barium is leached out as barium chloride (very nasty, but easily treated waste stream...) and rest of titanium oxohydroxide, which can be sometimes undissolved, is very porous and easily crushed even with glass rod directly in the beaker.

Also some types of modern MLCCs does disintegrate slowly in HCL, but I do not know precise compositions of these ceramics, as I didn´t work with them too often.

I mentioned it just as an option. I did performed several experiments with old types of MLCCs for the possibility of processing them by this wet route, but we sticked to the classic smelting due to hassle with lots of waste liquids and to the end - partial dissolution of PGMs from foils in large quantity of HCL (impractical). But I must admit, it is spectacular to watch how ceramic spreads out and leave the PGM foils/leafs in the acid After sucessful dissolution of ceramics, all space in the liquid is occupied by foils. Replacing the leachate with fresh HCL, heating and addition of nitric - vigorous reaction (large surface area) and after two or so minutes, bloody red liquid appear... Never gets old I will do this (altough not the most efficient process) from time to time on small batches just for my own "pleasure" to watch this very colorful process. Leachate from ceramics is usually purple/blueish in colour (titanous chloride ? or PGM nanoparticles from dissolving solder... we do not precisely know), but when it is left exposed to the air, it will turn green due to dissolved copper from legs. Ceramics are milky white, and then AR dissolution of foils bloody red

 

[sayf]

Concentrated Nitric will dissolve Pd.
If you have Tin use HCl first, it will dissolve the Tin and most if not all the Nickel.
Filter it and wash the powder well, roast them and then go for Nitric, but use dilute Nitric, to reduce dissolving too much Pd.

Hi and thanks for your reply, i meant there that am gonna skip the step of base metals leaching, instead ill go directly to hot concentrated nitric acid to leach palladium and all other base metals , in this case tin will be turned into metastannic acid and ill get rid of it using the filtration so at the end of the process there will be copper, palladium, and silver in the solution (since nickel is insoluble in concentrated nitric acid)
Silver will be precipitated by hcl then the Solution is filtered to have mostly copper palladium solution
after that ill adjust the PH to a value between 2and3 to precipitate the palladium by formic acid

After this process is done ill go to aqua regia to make sure that all the values are leached completely as suggested by orvi

 

[Yggdrasil]

Hi and thanks for your reply, i meant there that am gonna skip the step of base metals leaching, instead ill go directly to hot concentrated nitric acid to leach palladium and all other base metals , in this case tin will be turned into metastannic acid and ill get rid of it using the filtration so at the end of the process there will be copper, palladium, and silver in the solution (since nickel is insoluble in concentrated nitric acid)
Silver will be precipitated by hcl then the Solution is filtered to have mostly copper palladium solution
after that ill adjust the PH to a value between 2and3 to precipitate the palladium by formic acid

After this process is done ill go to aqua regia to make sure that all the values are leached completely as suggested by orvi

Most members here goes to great length to avoid meta stannic acid.
It’s not something to just filter.
It is on the verge of not filterable.
And since a soak in HCl will solve the problem quite quickly, I’d still do that first.
But it is up to you how you decide to run it.

 

[sayf]

Most members here goes to great length to avoid meta stannic acid.
It’s not something to just filter.
It is on the verge of not filterable.
And since a soak in HCl will solve the problem quite quickly, I’d still do that first.
But it is up to you how you decide to run it.

Yeah i already followed your advice, they were in HCL, and diluted nitric is the next step to get rid of copper, iron, and hopefully nickel, but tbh am worried that (20%) diluted nitric will dissolve lot of the palladium since the MLCCs are finely powdered.

 

[sayf]

Yeah, nitric dissolve bare, exposed Pd, but from my experience, platelets of ultrafine foils of Pd between layers of ceramic are very difficult to strip of values completely with nitric alone. That is why we completely abandoned "wet route" for MLCCs in classical terms of soaking the vigorously stirred powdered MLCCs in ntric. Without decomposition of ceramic matrix, it took ages for them to dissolve, even in hot solutions, and ceramics hold the values adsorbed onto the surface. HCL does much better job in destructing ceramic matrix, so AR leach is in my opinion necessary as second step.*

Owltech has relatively recently posted great video on processing old Bulgarian MLCCs by "wet route", altough he dissolve ceramic matrix firstly with conc. HCL - which also took with it base metals from the solder, and also somehow copper legs too. Mystery to me how copper can be dissolved in just HCL, but it is clearly happening in the conditions used, together with prolonged boiling. Important to say, if base metals dissapear from the solution, HCL also leach some Pd into the solution just by itself. So testing with stannous should be advised.

*edit for clarification: not all types of ceramic are decomposed in hot HCL or AR. Easiest to disintegrate and eventually dissolve are BaTiO3 ceramics found in old MLCCs. Altough some modern types are also attacked.

Most members here goes to great length to avoid meta stannic acid.
It’s not something to just filter.
It is on the verge of not filterable.
And since a soak in HCl will solve the problem quite quickly, I’d still do that first.
But it is up to you how you decide to run it.

Hi, i started the process and followed your steps , tin was firstly remobed by hcl and after several washes i put mlccs in diluted nitric 20% until no clear reaction is happening.
After that the mlccs were put in concentrated 70% nitric on 80 Celsius temperature and left there for 4 hours , and of course the fumes were condensated using cold water
Any ways i filtered the nitric and added HCL and silver was filtered

I then added about 50 milliliters of formic acid to the solution and start adding caustic soda to get a PH value around 2 then i stopped the whole process because i got this fluffy precipitate all around the luquid at PH between 2 and 3
So is this normal ?
Should i proceed to the next step which is heating the solution or something is wrong
Thank you

 

[Yggdrasil]

Hi, i started the process and followed your steps , tin was firstly remobed by hcl and after several washes i put mlccs in diluted nitric 20% until no clear reaction is happening.
After that the mlccs were put in concentrated 70% nitric on 80 Celsius temperature and left there for 4 hours , and of course the fumes were condensated using cold water
Any ways i filtered the nitric and added HCL and silver was filtered

I then added about 50 milliliters of formic acid to the solution and start adding caustic soda to get a PH value around 2 then i stopped the whole process because i got this fluffy precipitate all around the luquid at PH between 2 and 3
So is this normal ?
Should i proceed to the next step which is heating the solution or something is wrong
Thank you

I have never used the Formic acid reduction.
The way you do it do not correspond of how I have seen it or read about it.
I think Sreetips show it in one of his videos.
And I think the precipitate should be dense black/grey powder.

Edit to add:
I found a nice video from Owltech showing the formic acid reduction.

 

[sayf]

I have never used the Formic acid reduction.
The way you do it do not correspond of how I have seen it or read about it.
I think Sreetips show it in one of his videos.
And I think the precipitate should be dense black/grey powder.

Edit to add:
I found a nice video from Owltech showing the formic acid reduction.

Hi, i think i followed the way that orvi used in his thread

 

[goldshark]

Just a quick note on ceramics. you almost have to assay them to determine wether they are high Alumina, high Silica, Titanium composites, etc., before trying to dissolve in the appropriate acid (s). Plus some hybrids I am not familiar with. Figure out the metal/ceramics logistic to determine which is the economical route.

 

[Yggdrasil]

Hi, i think i followed the way that orvi used in his thread

Did you watch Owltech’s video?

 

[sayf]

Did you watch Owltech’s video?

Yes i did, but he didnt get the same fluffy precipitate i got when adjusting the PH

 

[Yggdrasil]

Yes i did, but he didnt get the same fluffy precipitate i got when adjusting the PH

He got the right thing.
I haven't checked his video yet.
But I think according to the information in Hokes book, you need to adjust the pH first and then add the PM bearing solution into the boiling formic acid.

 

[Yggdrasil]

Yes i did, but he didnt get the same fluffy precipitate i got when adjusting the PH

I'm not entirely sure what you did, but he adjusted the pH until the Pd precipitated as an Hydroxide I guess, then he added the formic acid and started boiling/simmering until the liquid was crystal clear.
This increases the chance of bringing down contamination, since he took the pH all the way up to 4.
Have you read the writings on formate reduction in Hokes book?

 

[sayf]

I'm not entirely sure what you did, but he adjusted the pH until the Pd precipitated as an Hydroxide I guess, then he added the formic acid and started boiling/simmering until the liquid was crystal clear.
This increases the chance of bringing down contamination, since he took the pH all the way up to 4.
Have you read the writings on formate reduction in Hokes book?

In owl case the solution was mainly containing palladium , in my case i think i have nickel copper maybe some iron.
Orvi in his process put the formic first then took the ph up to 2 then he simmered the solution for 2to3 hours

 

[Yggdrasil]

In owl case the solution was mainly containing palladium , in my case i think i have nickel copper maybe some iron.
Orvi in his process put the formic first then took the ph up to 2 then he simmered the solution for 2to3 hours

Have you read the process in Hokes book?

 

[sayf]

Have you read the process in Hokes book?

I read lot of it but tbh i havnt read the formic part as i remember its somewhere in chapter 6